The Second Joyful Mystery: The Visitation of the Virgin Mary to Elizabeth

Commenting on Luke 1:39-45, the when Mary journeys to visit her cousin Elizabeth, St. Augustine of Hippo (+430) speaks of the infant John, to be known as the Baptist, leaping in the womb at the sound of Marys voice:

We see instances of leaping no only in children but even in animals, although certainly not for any faith or religion of rational recognition of someone coming. But this case stands out as utterly uncommon and new, because it tool place in the womb, and at the coming of her who was to bring forth the Savior of mankind. Therefore this leaping, this greeting, so to speak, offered to the mother of the Lord is miraculous. It is to be reckoned among the great signs. It was not effected by human means by the infant, but by divine means in the infant, as miracles are usually wrought. [ep 187.23]

Christ came into the world in "the fullness of time" (Gal 4:4). His First Coming was foreseen from all eternity and His Nativity was prepared from the beginning of the history of our salvation. The manner of His birth is significant. St. Leo I, "the Great" (+461; whose Christmas sermons deserve entries apart!) wrote in a letter:

His God in that "all things were made through Him and nothing was made without Him." (John 1:3) He is human in that He was "made from woman, made under the law". The nativity of His flesh shows His human nature. The virgin birth is an indicator of His divine nature. [ep. to Flavian 4]

As there is a fullness in things, so there is in time. For each thing has its fullness in a full and copious perfection that abounds in everything. Christ is the fullness of things. The fullness of times is the consummation of freedom. So that His fullness may be whole and perfect Christ collects His members who are scattered, and in this way His fullness is achieved. So in the same way the fullness of times was achieved when all had become ripe for faith and sins had increased to the utmost, so that a remedy was necessarily sought in the judgment of all things. Hence Christ came when the fullness of time was completed. [Epistle to the Galatians 2.4.3-4]